Among the types of attacks known to the person skilled in the art, it is possible to cite attack by probing, which entails inserting a probe into the interconnection part of a circuit so as to read the electrical signals emitted by the various components, and then to analyze them so as to obtain information on the operation of the circuit.
In order to protect oneself against this type of attack, it is conventionally possible to place a protection shield in the upper zone of the interconnection part of the circuit. The shield conventionally comprises metallic tracks in which electrical signals are made to flow. Thus, upon inserting the reading probe, the metallic tracks are impaired and the signals can no longer flow in the shield. The circuit can therefore detect an intrusion and, for example, generate an alarm signal so that appropriate action can be taken.
Another known type of attack is attack by injection of faults, which consists in injecting a fault, for example, with an electromagnetic injection coil generating an electromagnetic radiation, in such a way as to modify, for example, the value of one or more bits of a temporary result of a computation without impairing the physical integrity of the circuit.
An analysis of the behavior of the circuit in response to these injections can make it possible to obtain secure information such as, for example, cipher keys.
Ways exist for protecting oneself against this type of attack, such as, for example, cryptographic computations comprising multiple verifications of the computations performed.
However, these schemes can be circumvented by more elaborate fault injection schemes, such as, for example, attacks by double injection of faults.